The present invention relates to a process for assembling a group of elements comprising at least one first element and one second element, one of the elements comprising a microstructure without package.
As is known, hard disks are the most commonly used data storage solution; consequently they are produced in very large volumes, and the maximum density of data storage is increasing year by year. Hard disks are read and written by actuator devices, the general structure whereof is shown in FIGS. 1 and 2, and is described hereinafter.
In particular, FIG. 1 shows an actuator device 1 of known rotary type, which comprises a motor 2 (also known as a voice coil motor) secured to a support body 3 which is generally known as E block, owing to its xe2x80x9cExe2x80x9d shape in lateral view (see FIG. 2). The support body 3 has a plurality of arms 4 which each support a suspension 5 formed by a cantilevered plate. At its end not connected to the support body 3, each suspension 5 supports a R/W transducer 6 for reading/writing, which in an operative condition is disposed facing a surface of a hard disk 7, so as to perform roll and pitch movements in order to follow the surface of the hard disk 7. To this end, R/W transducer 6 (which is also called picoslider or slider) is bonded to a coupling called gimbal or flexure 8, which is generally formed from the suspension 5 and comprises for example a rectangular plate 8a, cut on three and a half sides from the plate of the suspension 5, and having a portion 8b connected to the suspension 5 and allowing bending of plate 8a caused by the weight of the R/W transducer 6 (see FIG. 3).
For increasing the data storage density, it has been already proposed to use a double actuation stage, with a rougher first actuation stage, including the motor 2 moving the assembly formed by the support body 3, the suspension 5 and the R/W transducer 6 across the hard disk 7 during coarse search of the track, and a second actuation stage performing a finer control of the position of the R/W transducer 6 during tracking. According to a known solution, the second actuation stage comprises a microactuator interposed between the R/W transducer 6, as shown in FIG. 3, which shows exploded the end of the suspension 5, the gimbal 8, the R/W transducer 6 and a microactuator 10, in this case of the rotary type. The microactuator 10 is controlled by a signal supplied by control electronics, on the basis of a tracking error.
The microactuator 10 comprises fixed parts and suspended mobile parts. In particular, the latter, during assembly of the R/W transducer on the microactuator and when forming connections with the control circuitry, may be displaced and/or may collapse. In addition, stresses may be set up in the structure of the microactuator, such as to cause fragility of the structure.
In order to keep the final assembly process similar to those used before the introduction of a dual actuation stage and at the same time prevent displacement and collapse, systems for protecting the microactuator have been proposed, which, however, are complex and consequently costly.
The disclosed embodiments of the invention provide an assembly process that enables protection of microstructures when assembled on other components in a less complex and more inexpensive way.
According to the embodiments of the present invention, a process for assembling a group comprising at least one first and one second element and a unit thus assembled are provided, including a microstructure without package, the process comprising: forming a first wafer of semiconductor material having a plurality of microstructures including first and second operating regions separated from each other by first trenches; forming a second wafer of semiconductor material comprising blocking regions connecting a plurality of first and second intermediate regions, the first and second intermediate regions separated from each other by second trenches; joining the first wafer and second wafer to form a composite wafer wherein the first operating regions are fixed to the first intermediate regions and the second operating regions are fixed to the second intermediate regions; cutting the composite wafer into a plurality of units, each unit including at least one first operating region and one second operating region, and one first intermediate region and one second intermediate region; fixing the first intermediate region of at least one unit to the second element; and removing the blocking regions.